Understanding Espresso: Pressure (Episode #6)

[@benstrong445]

Got my job as a Barista because of this guy! ☺️

[@pokefirerex]

I became a better barista because of this guy!

[@benstrong445]

I should also add I had to become a barista to keep up with understanding his videos, content gold!

[@vtsormpa]

I want to become a barista because of this guy!

[@cameronlackey7301]

I converted my barista career into a bit of a fanaticism thanks to this guy lol 😆

[@_sootyfoot]

Good luck in your career dude 🤞

[@miguelantoniogonzalezceden994]

I started watching this channel for a French Press Recipe. 3 SCA Certifications and a Pandemic Later, I am about to start a part-time job as barista while finishing a Master Thesis in Chemistry. Still come to this channel to listen to the British soothing voice of James and enjoy coffee stuff :)

[@caseybowman9017]

Hey friend! May I ask where you are now a year later? I’d love to hear what you’ve done!

[@CoffeeReviews]

This is a really impressive breakdown. You can hear the knowledge, passion and enthusiasm for a pretty complex subject. Amazing work as always James

[@morenasisro2054]

se p oo oo

[@morenasisro2054]

por o

[@williamadam995]

Hi James, another explanation for pre-infusion is as follows: First of all, each puck of coffee has a voids, moisture, and solids. The moisture content is likely really low to start off so lets just consider the voids. These voids are only air-filled to start and thus are susceptible to compaction under any pressure. The 9 barr pressure will do this. However, from my knowledge, if water was filling these voids(pre-infusion), this would have a closer to equal hydrostatic pressure pushing back which would then be replaced over and over by the pressurized water passing through the puck. This is only from my limited knowledge of fluid mechanics and how sands in foundations pack together but hopefully, this helps a little bit.

[@paulomarques1795]

Yes, yes and yeas once more. Nicely explained!

[@Spractral]

Very well described. I don't understand enough about physics etc (yet) but when picturing this it makes sense to me intuitively. I'm glad I got a flair and just recently got a better, more reliable (manual) grinder to go along with it. I'm starting to make some great tasting espresso.

[@paulomarques1795]

@@Spractral Puck preparation is key for good espresso extraction. It's all in how those grounds!

[@ROckNCom]

I think his point is that the lower pressure preinfusiin helps to fill the voids with finer grounds thereby reducing opportunities for channeling

[@s0bad]

So you're saying longer pre infusion is better?

[@econnormist3837]

I know you said it was the last episode of the series, but I'd be super interested to know how the coffee itself is a variable. Particularly how the variety, process, age and roast all effect the other variables you covered. Maybe a future weird science episode?

[@overlordcontents7293]

This is actually very lagit and shouldve been covered. Not before then it would be obsolete datas but then once you know how to work with variables regarding espresso it will be a lot more easier to understand the roast type, varietals and flavor profiling.

[@overlordcontents7293]

Also I've realized that a general consensus around the world who try to get into this coffee world is by being a barista. And getting to know through that perspective to see the whole new world . What an exciting time. I'm loving it.

[@steinanderson9849]

@@overlordcontents7293 *legit

[@person9513]

Now that i understand espresso, i need to learn how to make enough money to get an espresso machine

[@doctormoobbc]

Flair neo could be a good entry level "machine"

[@phil6904]

@@doctormoobbc yes, Neo is definitely an affordable start point. I upgraded by adding the pressure gauge and the non-pressurised portafilter very quickly though. Allows for much more control, while still affordable.

[@xSLWRTHNUx]

Are you feeling the pressure to buy an espresso machine?

[@person9513]

@@xSLWRTHNUx haha

[@Michael-ff7yl]

Flair Signature, you want that pressure gauge, then experiment to your heart’s delight :0)

[@tallbikercat]

As an engineer, pressure is a result of flow against some sort of constriction (Cv). This Cv is usually used to determine pressure drop within a system (piping), but is also influential on the standing pressure behind the source of constriction. In the case of your espresso machine you have two constrictions...the primary constriction being the puck, and the secondary constriction being the orifice prior to the puck (for your pre-infusion). The orifice is a fixed constant as the size of the orifice never changes, scaling aside. The puck on the other hand is a highly variable constriction point and can be influence by a multitude of variables...grind size, grind uniformity, tamping force, oil content in the beans, moisture content of the beans, roast, etc. The result is that you can have a wide variance in flow rates at a given pressure depending on the variables affecting the constriction seen at the puck. If extraction is primarily a function of contact time, and to a minor degree pressure (as pressure affects solubility of various components, as does temperature) I would intuitively think that flow (your output) would be your primary control point regardless of other factors. Fine tuning the other factors (grind, tamp pressure, etc) affecting you puck will only improve you extraction from there, but get the flow proper first regardless of the pressure.

[@samroesch]

100%... well 99%, extraction being based on time is not so straightforward. The velocity of the water affects the extraction, hence flow rate being important in of itself.

[@pirminborer625]

As an engineer I agree. Also you have to account for dry puck is not wetted well because of water surface tension (like a soil). If immediately applying pressure a lot of porosity is not available, because surface tension resistance is less for bigger pores (less compacted paths or with less fines), forcing water trough the easiest paths. This less resistance paths get even higher flow rate when solids are disappearing during extraction leading to channeling. The best way is really to let the puck soak itself. You can see this on a naked portafilter when coffee starts uniformly to push trough. Preinfusion is key. You cannot get uniform flow trough a dry puck. The best in my opinion would be to have lower temp water for preinfusion allowing for really long preinfusion times without starting the extraction process.

[@samroesch]

@@pirminborer625 Dude, nice... I’d never considered the surface tension! That makes so much sense, but I don’t think anyone in the coffee world knows this, all I’ve ever heard is what James said in the video.

[@humphrey2703]

I totally agree with you. I believe contact time and flow are more important than pressure. Unfortunately, there are only a few (very expensive) machines out there which let you control flow instead of pressure. Constant pressure can be achieved in a very easy and cheap way but constant flow requires more expensive equipment. Pressure profiling is, in my opinion, just a workaround for flow profiling (e.g. the lower pressure during pre-infusion is not the most important variable but the lower flow rate and contact time is. Yes, the lower pressure during pre-infusion decreases the compression of the puck, but this is not a value in itself). Flow profiling, on the other hand, would give us the best control about the extraction I believe (a lot of assumptions as I don’t own a flow profiling or constant flow espresso machine 😉). For the perfect dialed in espresso you could probably end up with the same initial pressure, flow and contact time (or at least similar values). But even then, I think flow profiling will increase consistency from shot to shot. Let’s say the grind size changes because of a change in humidity. For a conventional espresso machine, you have to choose than between keeping the brew ration or the contact time constant (or throw the espresso in the sink and try again with a different grinder setting). For a machine that controls flow both flow and contact time will stay the same (but the pressure will be a bit different of course). I believe the second scenario does not change the extraction as much as the first scenario (while keeping the brew ration fixed). I would love to see more espresso machines on the market in an affordable price range. Does someone have a flow profile machine and can tell me from experiments and experience if my assumptions are right or wrong?

[@samroesch]

@@humphrey2703 This is what the Decent espresso machines do.

[@MrHarlequin2316]

This time last year I thought coffee was a hot drink and certain high street chains did posh versions. Then I saw James saying “don’t get an espresso machine unless you want a new hobby”. It’s not a hobby, it’s an obsession and with each video I’m going deeper down the rabbit hole. However, I honestly believe that it, and in particular your videos have helped keep me (relatively) sane through this period, so thank you. Off to pull levers and dream of an iPad version of the Decent ☺️

[@McTAnGuS]

Anyone else have family and friends that ask for a coffee then when they oh wow that was amazing you dive into the details and they are like yeh next time I'm going to ask for tea. Thanks James ☺️

[@bspark119]

Can’t believe James mentioned fines migration. This is a fairly well understood concept in Earth Science (Soils and Geology) and just reinforces the idea that Coffee, Espresso in particular, really is a science as well as an art.

[@paulomarques1795]

Soil mechanics at the service of espresso extraction!

[@southboundaustral]

Earth Science deals with the greatest pressures on earth from volcanic activity, to plate tectonics to various load bearing mass. With soil, sands, minerals, chemical bonding and reactions, silt transportation over various mediums, sifted through various mediums. Are there particle dynamic models that are explicative of coffee and water transportation profiling. If not that something analogous?

[@itsme5625]

Me on my Aeropress: ahh yes im reaching 9 bars

[@crzxm]

Haha!!

[@sebastianvaldivieso9654]

For reals!

[@BensCoffeeRants]

People have actually tried but yeah you can't get anywhere near that much pressure. Aeropress is great though.

[@SebastiaandeBeer]

Andy Serkis as Barista: ‘MY PRESSURES!’

[@treyrees9153]

I would love a retro review series where you show us all the important espresso machines from throughout the decades. We'll be able to see how the machines developed over the years to achieve better espresso

[@pirminborer625]

Watching this while pulling a shot on my la pavoni, while I was preinfusing and then ramping gently the pressure up, then maintaining flow rate, hoffman starts to talk about pressure profiling and adjusting for flow rate. Wondering if one day an automatic machine could do that. It's not just flow rate but you can see if you got good crema, chanelling or uneven extraction. I adapt for it. Certain shots you can maintain the pressure quite high, with evenly distributed flow with tons of crema. You feel and see when you pull that perfect shot. Other times you have to compromise, but it still can taste very good. Even if it's more work a manual lever, the feedback you get is priceless and you really learn a ton about coffee extraction intuitively.

[@KyleRowsell]

Excellent video as always James! I flow profile my espresso daily on my Lelit Bianca. It has a needle value Flow Profiling paddle to adjust flow at the group head similar to a slayer steam. I love long pre-infusions, then ramping pressure up and finally backing down to about 6ish bars for the final 5-10 seconds to reduce over extraction. It’s been working well.

[@movieman77777]

I’d love a video on the Lelit Bianca. Such an interesting machine

[@pavelkaiser6787]

Hello I just purchased Lelit Victoria. Would you know whether there is also a chance to manage the flow profile? I am just learning the basiscs so any advice will be very much welcome! Thank you, Pavel.

[@tlniec]

I really resonated with James' discussion on early lever machines and how they produce what I'd call serendipitous pressure profiling. It's always interesting when this phenomenon is seen in engineering - a new innovation makes an obvious improvement by design (faster brewing in this case), but also has unforeseen off-target effects that make it even better.

[@JanHaHe]

The new upload frequency is such a treat. Love your content James!

[@BiggFanDDD]

I got a Flair (first espresso machine ever) and I've gotta say I absolutely love it! James's recommendation and review was excellent! Since I'm a total espresso noob, I don't know too much about pressures, but I have noticed that with higher pressures (around 9-10 bar) I often get quite a bitter brew, but with 6-8 bar I get the perfect cup.

[@edmichaelson6890]

Whew!! Here is my take: (BTW Enjoyed the video) There are so many variables -Different beans -Age of bean -Storage of bean -Grind size -Grind amount -The roast -Weight -Volume -Type and shape of basket -Type and hardness of water -Temperature of water -Tamping force -Extraction time -Extraction pressure (and pressure/flow profile over any given extraction time) So you see where I'm going here You're either a lumper or a splitter or somewhere in between Practically speaking there are too many variables to address or over which you may not have control You can get a good shot out of most beans making adjustments if necessary as the beans age In fact you can get almost identical shots with different sets of settings Sort of like cooking good results roasted, grilled, fries broiled, sauteed , sous vide Not totally unlike wine e.g. vintage year, storage temperature, grape, color, nose, bottle size and with hints of black current, raspberry blah blah Bottom line you either like it or you don't (although someone else might) If you don't - tweak

[@ruisearts]

My country is in ruins, our currency is devalued in record-breaking hyperinflation, and I'm here listening to James explain pressure, learning moreover what I have studied. Like a scene in a film where it's the end of the world outside the window, and I'm inside listening to a beautiful record.

[@severini8153]

Where you at?

[@ruisearts]

@@severini8153 Lebanon

[@severini8153]

@@ruisearts good luck Richard!

[@ruisearts]

@@severini8153 thanks

[@funkyguy99]

Do you have any gold and silver? If not, then get you some!

[@graemeshearer9718]

I dropped the pressure on my machine to 6 bar about a month ago on the recommendation of another barista. It seems to produce much more consistent, sweeter tasting shots, probably due in part to less risk of channeling as James said. Watched this nervously, wondering whether he was going to call out people for brewing at 6 bars haha.

[@erharddinges8855]

And what does this mean for timing?

[@Maratsi]

@@erharddinges8855 I’m trying to find answer as well about the extraction time

[@1birchswan]

I have a niche zero, and a La Pavoni lever machine with a pressure profile gauge. When the group head reaches 90c, I raise the lever and purge a little air and water, before inserting the portafilter, then start the pre-K fusion, and wait for coffee to drip before starting the pull. It might be 10 or up to 40 seconds or more. Then the pull is relatively short, until the output is twice the input.

[@lostintheworld12]

Any insight on pressures above 9 bar would be super useful. The new model gaggia classic pro brews at 12-14 bar and I for one would love the know: A) why? B) are there upsides to higher than 9 bar pressures? C) are there major downsides? D) what product you use in your hair

[@chookchack]

To my understanding this is to accommodate users who use pre-ground, store-bought coffee and utilizing the pressurized basket. I modded my gaggia classic pro pressure a week after i got it new and installed a pid 2 months after, that was just two days ago. Lol

[@BensCoffeeRants]

I think a lot of people mod it so it does 9 bars (or sometimes 6). I think they say you're more likely to get channeling if the pressure or flowrate is too high. I think you'd end up with a more intense likely bitter and less than balanced shot usually. It COULD work well with certain lighter roasts depending on your tastes maybe.

[@chookchack]

@@BensCoffeeRants with high pressure you have a small room for error in your puck prep. You’ll get channeling unless you distribute the grounds perfectly.

[@tusokpoweru]

is there a benefit for going up to 9bar? I hear that 6bar is the sweet spot for consistent and best tasting espresso?

[@BensCoffeeRants]

@@tusokpoweru might be easier to work with 6 bars but I think 9 bar is probably going to have more intensity. Also not that it matters but I don't think it's technically espresso unless you're hitting 9 bars. Before I really knew what I was doing I played with my machines opv settings a bit. Found 6 bar was nice but lacking intensity kinda boring. 10 bars was more bitter and intense but that also could have been because I had poor coffee prep back then and was just getting channeling. I think I kept it at 8 bar for a while and liked it there.

[@mattkinsella9856]

I only just started getting into HOW to make decent coffee and this channel has been a godsend. Just from drinking coffee and trying different types and many failed attempts at home to make good coffee, I knew there had to be a lot more to it than paying more for coffee beans and crazy money on better machines. I wish I'd had access to this information 10 years ago, I'd have been drinking better coffee a lot longer and I don't even want to think about the money I would've saved.

[@JLRocco43]

As someone who expects to retire and then probably owning a local coffee shop. Thanks for the content, James :) I've been binge-ing your videos for a few weeks now

[@willmitchell8500]

please dont. just relax and ENJOY being retired.

[@GlenEdwards]

Exactly, owning a coffee shop is only going to be “retired” if you hire someone to manage and other to run it. It’s a LOT of hard work and stress.

[@qsmlj]

I believe we didn't touch on the effects that pressure has on the body of espresso. If it does which I don't really know. Also would you be so kind to answer if the amount of pressure has an impact on what can extract from the ground coffee and what can't? From my chemistry classes I remember something along the lines of: pressure allows/is required for certain chemical processes to occur. Thank you very much for the coffee knowledge and overall great experience I get watching your videos!

[@joechienjoe]

I am a la pavoni lever machine user For darker roast beans I use 7 bar and 23 second extraction time, most of the time this will make esspresso more favourable than normal 9 bar 30 second setting, worth a try guys, and thanks for making this video

[@Jay-gc7pp]

Other baristas started hating how pedantic I got since watching James

[@denmcx6538]

James, I've to say, yours is the ONE AND ONLY of my subscribed YT-channels, I watch and listen to with the speed setting @ 1,00...

[@Narezaath]

I think there are some things worth mentioning: 1) Sage/Breville-style preinfusion for machines equipped with vibratory pumps: adjusting the power going into the pump allows for preinfusion with a % of pump's force, which is simple and effective. Oh, "but it adds electronics to my clean looking machine!"... said people with PID's and digital built-in shot timers, sometimes installed by themselves. I'm actually baffled how virtually no manufacturer does that, considering it's such a draw. Hell, make the scale constant! 2) machines like Lelit Bianca or others with special "paddle" for E61 grouphead allowing for pressure adjustment are also something to consider. They allow multiple pressure profiles (like lever) found on much, MUCH more expensive machines like Rocket R 9 One (which is a mouthful) for a third of the price, but with (arguable) disadvantage of having to adjust the pressure manually, through a "paddle". 3) Mark from WholeLatteLove presented multiple pressure profiles, like lever-style, 2nd-stage jump and the like for different shots and with explanation for how and why. Worth checking out, in my opinion. (Not paid to inject, but wouldn't say "no" to free money, heh) also, if this goes on I might actually find a side-gig as a barista. :)

[@LuckyDragon289]

You're making the mistake of equivalating pressure with flow... machines like the Bianca and the WLL videos (incl the Dalla Corte Mina) are not about pressure profiling, but flow profling. That is, controlling flow (in g or mL/s) as the input variable. Those kinds of machines maintain a fixed pump pressure and the user adjusts an aperture near the grouphead that restricts the flow of water. The Rocket R9 One is a pressure profiler because it adjusts the voltage sent to the rotary pump that changes pressure.

[@Narezaath]

@@LuckyDragon289 It is true that pressure at the pump doesn't change. HOWEVER the pressure the grouphead does, which can be seen with a manometer in E61 installed on said grouphead. While adjusting the flow, the pressure at the puck changes, which makes sense since less water is let through, exerting less force on constant area, lowering the pressure that is put on it.

[@timb15]

@@LuckyDragon289 is there not an impact on pressure hitting the puck when flow profiling

[@tobymarol7329]

That's the beauty about a Pavoni or similar manual lever machines.. when you feel decreasing resistance from the puck you automatically pull back the force since you don't want to rush the lever through. It makes one instinctively follow all the advice you give in this video, just by feel.

[@NitinSharma-vs8jt]

Hi James, it was quite a comprehensive video, although the La Pavoni did deserve a mention in this video as one of the oldest and most popular lever machines with the ability of pressure and flow profiling (and pre-infusion as well)!

[@bartpeterleroy932]

I have seldom seen such excellent teachers like James Hoffmann. Incredible. Thank you!

[@GrantMcWilliams]

This is very useful for those of us with lever machines, we can vary the pressure however we want. I usually bring it straight up to 9 bars and leave it there until it's done. I will start experimenting with different profiles.

[@maxlee6676]

try ramping up to 2 psi and hold it there for the first 20 seconds, then ramp up to 9 psi, and after like 5 seconds, slowly start to ramp down to 6 psi by the end of the shot. that's how I do it

[@GrantMcWilliams]

@@maxlee6676 Which lever machine do you have? I've found with the Espresso Robot the puck likes to lift at low pressure (pre-infusion). I was thinking of having a machine shop make a new basked without the rounded bottoms.

[@maxlee6676]

@@GrantMcWilliams I'm using a flair signature, and the bottom of the basket has a small concave, but I haven't had any issues with lifting. I just get a few drips at the beginning, but I just go on with it. are you maybe releasing some pressure during or after pre-infusion? with my flair, in order to maintain 2-3 psi (I actually usually go with 3 psi, I only said 2 psi because you'll get less drips at the beginning), I actually press down on the lever very slowly while watching the pressure. I don't really think I've experienced lifting.. so im not really sure what to do about that

[@GrantMcWilliams]

@@maxlee6676 Thanks, I think the issue is the edges of the Robot basket are rounded and the water finds it's way around it. My puck doesn't lift unless I try to pre-infuse and other "more experienced" robot users said it was because of the shape. I think if I start out slow and increase pressure in a sort of preinfuse then it might be fine. I'll try that.

[@BensCoffeeRants]

@@GrantMcWilliams sounds like the robot needs a new gasket?

[@daysofseptember]

Would love to see an espresso machine showdown (kind of like the ultimate grinder week) very curious to see something like the LM Linea Mini go up against the Decents.

[@maxw4259]

He needs to do a range of £500-1000 for people who can spend more than the machines under £500 and are almost at a commercial standard

[@daysofseptember]

@@maxw4259 would love to see it go even higher, there’d a lot of content on YT in that range but barely any higher.

[@AllaMortify]

@@daysofseptember Well, if you're going to buying a LM Linea Mini, ACS Vesuvius or Rockey Nine One you presumably know what you're doing. That's not likely to be very many people viewing his channel. If you haven't spent the time to learn what you're doing and just want to be able to say you have an expensive machine, then frankly you're an idiot wasting your money trying to walk before you can run.

[@edwardo5555]

As the owner of a E61 Hx with vibe pump, I’m always debating in my head whether a machine upgrade will produce far superior results. World LOVE to see a video on this

[@nickel_las]

I don't know whether James would do that because it may be a conflict of interest; James works with Victoria Arduino, who make commercial/prosumer home espresso machines, who compete with La Marzocco.

[@tauronmaikar]

Going to pull some shots on my Flair and ease the pressure a bit to see if I can mitigate channeling.

[@danymeeuwissen5973]

That definitely works! If you keep the needle high in the last third of your shot, there's a pretty big chance of channeling once the puck breaks down. I agree with James, on a Flair it feels intuitive to smoothly release pressure.

[@maxlee6676]

I also ramp up the pressure from 0 psi to 2 psi and hold it there until 20 seconds is up, then ramp up the pressure to 9 bars, then slowly back off to 6 psi by the end of the shot.

[@Richard.Mayston]

Definitely works. This is the major reason I'm sticking with a Flair and don't want a Decent/Rocket/Slayer. Use a mirror, a machine can never respond to the changes in pressure required the way you can see and feel it. Put your money in the grinder, my KafaTek Monolith Flat MAX is on the way.

[@maxlee6676]

@@Richard.Mayston i can't wait to buy an expensive grinder for my flair. i love it so much, and I'm currently on the niche

[@jacobbellman9832]

James, you are a true inspiration and a wealth of knowledge! I will say, as a newbie to the world of espresso I was a bit confused by this video. I just watched Lance Hendrick’s series on espresso and he described the relationship between pressure and flow rate in the reverse order. From my understanding from Lance, the OPV valve maintains a fixed maximum pressure, but other than that pressure is an output of puck prep (including grind size) and flow rate. It sounds like you are saying flow rate is actually dependent on pressure. I apologize if I’m missing a key concept or misinterpreting your message. I am in the market for my first espresso machine this year and I’m trying to learn all I can. Thanks again for such amazing content!

[@thinkbrowner]

So it's really funny. You just managed to put into words a lot of the stuff I found myself doing reflexively as I've practiced and improved my shots with the flair. I think a fully manual machine like that is actually probably a really good teaching tool when it comes to espresso

[@stevenflier7315]

Flow = k(pressure/resistance). This is a physical relationship where k is a constant unique to the system. You can also describe this as flow is proportional to pressure divided by resistance. The higher the pressure the higher the flow at a given resistance (and vice versa) and the higher the resistance the lower the flow (and again, vice versa). In medicine we use this to understand blood flow as it relates to blood pressure and vascular resistance. Helpful to keep this in mind for those who do pressure or flow profiling. I do not, since i use a Breville (sage) oracle touch- having taken to heart James’ comment in his review that it was good for those who did not want to make espresso their new hobby. Just a source of pleasure. James- thank you for these fascinating and enjoyable videos. Although espresso is not my new hobby, watching these IS. Cheers from Boston-

[@carbon5261]

I was talking to my mom about her dreams of home espresso and the new Flair 58, she said let's let a few people try it first "like your friend with the swanky hair", meaning you 🤣

[@otsoko66]

One thing I wish had been touched on -- having used manual and spring levers, as well as electric pump machines, I really prefer the coffee from the levers because it seems / tastes more complex -- there's more going on in the cup. I have always assumed that this is because the extraction at different pressures brings out different notes. [easy repeatability with a spring rather than a manual lever is the big plus for spring-lever; playing with the pressure is the big plus for manual levers.] Pre-infusion happens naturally with a spring lever (hold the lever down for 8 seconds or so before you release it), and is easy to do with a manual -- give it less pressure as soon as the water enters the piston. I never found a way of doing this with an electric pump - except turning it off briefly, which does often mess up the puck.

[@Drewinvan]

James is helping me really enjoy and appreciate coffee and also empty my wallet...but wouldn't have it any other way..cheers from Vancouver Canada, James. Keep up the great work!

[@dingnextstop]

Hi James, I have a Gaggia Classic 2010 which I bid and won on EBay sold as “ not working”, after stripping, cleaning, replacing seals, adding a DIY PID, pressure Gauge, Rancilio wand, bottomless portafilter with IMS basket and shower screen… ( sharp intake of breath)… it now works… phew… I’ve also invested in the basic Eureka Mignon Manual grinder, I have been plying with pressures and around 7-9 bar seems to be the sweet spot with Grinder dial set at No.1… it still isn’t perfect but i manage an 18g dose in with 36g out at about 28 seconds… using Papa New Guinea fresh beans… I’m still not 100% happy with the taste yet but I love tinkering with the pressures and grind size… thanks for your educational videos… Andrew

[@snakeriveridaho33]

Hi James! I love your channel! Seems like you should have discussed the Mina in this current video. Take care, Kirk

[@n00baTr00pa]

Now he has to do an e61 video!

[@user-qw8fe6wp7k]

I would love to think that James will make this kind videos for other 50 years without running out of topic! We should start to number each lesson and start watching them in chronological order and then take a compulsory exam! How fail it, can drink only Starbucks coffee !

[@Prolitiker]

I really love this series and how concise and methodically clean you break down complex topics. Thanks James!

[@lorincapson7720]

Espresso fascinates me and frustrates me. I get to try every day to make the best tasting shot. Every day I get a different experience.Thanks so much for your videos.

[@FelixWidjaja]

My routine in Bezzera Strega is just 6 seconds of pre-infusion (holding back the lever to make the pump stop); wait til I see a small drip in the glass, then go back to "turn on" the pump to re-fill the brew chamber with water (some were absorbed in pre-infusion process earlier), watch for a stream of liquid coming, then I release the lever and beging the extraction by lever. Usually I got a good tasting espresso.

[@doc8125]

Been looking forward to this one, love your work James!

[@johndododoe1411]

In the last week, KZbin channel "The Hydraulic Press Channel" had fun making 1000 bar espresso using mostly custom tools . It would be fun to see your reaction to their method, as it clearly goes against your explanations in this video from 3 years ago.

[@evanlawrence5815]

Would love to see you dial in a coffee on the used budget set up and then again on a commercial machine. Same bean. Just to talk about differences. Or even have someone else do it in tandem and you compare results idk. Think that there is some value in that

[@juanhamilton_]

I dunno man, there might be some value. But from my experience, the same principles apply to dialing at home vs commercially. It's all a limitation of your equipment, but that also can help inform how to accomplish the dialing process. There are some general guidelines, like "Dose makes the biggest difference in flow" and "Adjust grind size to taste, and then subsequently re-adjust dose if necessary after seeing a shot pull with the new setting" work both at home and in Cafes. The big differences come down to speed of production. Most people generally have more time at home, and during a rush, we gotta be getting coffees out at 1 every 45s-1m.

[@soidus]

Thanks to James, I decided to get myself a Gaggia Classic Pro and modify it to increase its capabilities. Can't say I'm a pro yet, but definitely I'm happier than when I had the DeLonghi Dedica.

[@The_Real_Vasily]

Thank you so much for the video! For a single boiler home espresso I open a stream valve to decrease the pressure. It helps to keep the flow more consistent in case of channeling.

[@LarryShwang]

James! Please do a video on pre-infusion. Timings of shot pours, effectiveness etc. That would make may year for sure. Thanks James.

[@januslin4995]

This is really an amazing series that help me to understand the such complex process of espresso making in a clear way. It’s really hard to determine how far the explanation should go or hold. James makes a preface balance.

[@ANTheWhizkid]

As you said, it´s a tough task to figure out a reproducable method of making a better espresso without just only making a different espresso, the more variables you can influence. But it´s just so nice to have these variables and to play around with them like you´re on a treasure hunt. Great content James!

[@Dirtyz1234]

Video is reminding me about the pressure gauge I purchased to add to my Silvia. I usually set it and forget it on the machines I've owned, but I feel like it's good to have an easy check for machine health.

[@frahorcz]

Just came and thougt I’d quickly browse through as with the other coffeetubers… and here I am 16 minutes later like “what, it’s over?” You are doing a really great job here, James!

[@ninal5027]

Just when some local coffee expert tried to discourage me from getting an espresso lever machine, here comes James with his awesomeness of knowledge and willingness to share it, and I'm back to the track 😌👌🏻👌🏻

[@frankocolumbo4244]

That “local coffee expert” is just terrible with lever espresso machines by the sound of it.

[@sitiesito715]

If you enjoy the grind of the learning curve, a lever machine can be very rewarding. If you buy second hand, are handy, and can restore an old machine, you can really save some $$. I can understand that some people don't like tinkering, but if you do, get the lever. I love my La Pavoni!

[@ninal5027]

@@sitiesito715 Thank you! I wanted to buy a second hand La Pavoni after James' video but it's not available where I live. These things are rare here and that contributes to wrong conclusions about this method of brewing. But I'm willing to learn, so I'll get one!

[@ninal5027]

@@frankocolumbo4244 Yes, well I put it that way since he was a little arrogant letting me know if his opinion. He is helping others, though I think you're right, and he's just bad with levers :)

[@HappyZappy]

I have an Oster Prima Latte, got a proper basket for it, and a manual grinder. I use it on manual and it has a macanical on/off type of preinfusion. I do agree with James that when I tap out my pucks I find the top half will come out separately. This video sheds light on why. Thanks.

[@81caasi]

So from a while back, I've taken your advice Mr. Hoffman of switching my dose to 14g, like in Italy, because less is more! This has lead me to tinker with Pressure, by opening up my Gaggia Classic. With a smaller puck, the flow rate increased, and my grind size came to a point that was too small. I researched to no avail, what pressure do Italians apply when pressing a 14g puck into 40+ grams of liquid? I dialed in the same espresso bean for 9, 8, 7, and 6 bars pressure. I found with lower pressure, espresso had a less harsh mouth feel and taste. If the pressure is too low, you risked losing that zipp or acidity(?)and a balance in flavor. I settled on 7 1/4 bar as it gives a softer/rounder(new flavors) shot of espresso still with enough zipp and flavor. (plus more room to play with at the small end of grind size) What pressure is custom in Italy for a 14g basket?

[@simonmonty7171]

How are you getting 7 1/4 bar? Cutting the spring? Used the 9 bar and now 6.5. Wondering how your more recent experiments are turning out to be.

[@erharddinges8855]

14g to 40g+? =this is almost a ratio of 1:3 Your style of espresso?

[@81caasi]

@@simonmonty7171 with Gaggia Classic, you can open it up and turn a specific nut, every 1/2 turn equals 1bar pressure of change.

[@shahidyt]

My first espresso machine is a Bezzera Strega, in 2012, that was a good investment. It got me in to the coffee hobby and I learnt so much. I do have a Mypressi Twist too, both great machines

[@mithunfan]

I was just watching all the videos in the series to understand what i can do better in my daily espressos, and this video came out! Thanks James!

[@RyanGazling]

Happen to see this as I was just enjoying an espresso shot. James you are the best sir 👌 💙

[@samuelfinnerty5767]

I have a Sage Barista Express. It can be hard at times to produce consistent shots. The pressure gauge doesn't tell you how many bars it is but does give you an indication of espresso range pressure to aim for. Found that the grinder didn't grind fine enough so adjusted the internal burrs. 18grams of coffee. A good solid tamp produces a pre infusion of about 8 seconds with shots pouring between 25 and 30 seconds. I find that it produces more than 2:1 with espresso out. Sometimes 18grams produces 45 or more out. Overall shots are pretty good. And good milk, or milk alternative, covers a lot of sins on the espresso end so nothing is ever wasted.

[@cb2593baller]

Got the Lelit Bianca recently and this has been super helpful

[@_tizzle]

Bravo James, I am fascinated with fluid dynamics,, and your video may be the new baseline for explaining pressure in a simplistic yet comprehensive manner. We met 1 year ago in NYC at Coffeest at the Decent Espresso booth as the pandemic was taking hold, so it is rather serendipitous that I am writing a comment on this stellar video today. My only request: I would like to see another video in this serious which explains the dynamic relationship between pressure and rate of flow. Someday, I hope!

[@RedRoverTW]

I use an ECM Synchronika with the flow control needle valve in the E61 group. I am obsessive about uniform puck prep and consistent grind, so I use a high-quality grinder, WDT, OCD distribution, and a self-leveling calibrated tamper to eliminate most variables. I primarily drink darker roasts. I have found that the natural 3-4 second preinfusion is desirable for dark roasts, but with SHB high altitude lighter/medium roasts featuring higher acidity, a longer preinfusion before ramping up pressure tends to tone down acidity while preserving the bright fruit/floral/sweet flavors. I usually gradually decrease pressure near the end of the shot to avoid overextraction. It's a fun thing to play with when I get a batch of beans that I feel could use experimentation to improve flavor. I had the pleasure of playing with a Dalla Corte Mina that has full digital flow control via a tablet. It was amazing, but that's a rabbit hole I'm not ready to go down. 😁

[@SnowBob302]

I made a shot on my Cafelat Robot right after this video ended. It tasted better than the last because I previously prioritized maintaining pressure even I noticed channeling. That change reduced an an unpleasant bitterness on a light-roast blend that I was having even with 20g dose and

[@haberdashery314]

I just got started with my new robot last week. Getting way over caffeinated trying to get good enough at it that I am not embarrassed to pull shots for my friends. How are you noticing channeling? The manual says that the puck often cracks _after_ the shot when pulling up the levers creates a vacuum, making 'puckology' impossible. I expect some sort of puckology is still possible, but it will be a sub-discipline just for the robot. Anyway, are you inferring channeling when you feel a drop in pressure or...?

[@SnowBob302]

@@haberdashery314 I agree with Paul and his explantations in the manual. Actually I was thinking about Paul’s comments on the “9 bar magic number” and how he recommends closer to 7 bar since he measured the actual group head, as opposed to pump pressure, in many many machines and found it to be closer to 7 bar. The Robot measures pressure in the portafilter so his suggestion is to shoot for 7 bar since that is the actual extraction pressure on other machines read 9 bar. As far as channeling, I notice it when I get a “spray jet” during extraction. You can notice it that during extraction or at the end when you see fine splatter around your cup. James mentioned this aspect in this video and showed a brief clip. I have seen that same effect while watching the extraction from below. Also I have noticed two weak streams instead of one strong one that I believe to be channeling as well. I noticed the largest jump in quality when I started to do preinfusion at about 2 bar until the bottom of the portafilter is saturated. This again I started doing to evenly wet the puck and get even extraction. Previously I would quickly try to ramp to high pressure and wasn’t very pleased with the results.

[@haberdashery314]

Hey @@SnowBob302 This kind of report from an experienced user is very much appreciated while I learn the machine. Yeah, a “spray jet” would be a clue wouldn't it.?

[@SnowBob302]

@@haberdashery314 it seems like part of your comment got cut off. I would point you to the Robot User Experiance thread on the Home Barista forum for the largest discussion about the Robot. Paul has been known to drop in on that thread and offer his insights. It will be overwhelming when you first try to go through it but probably every aspect of the Robot has been discussed there. I personally put in a lot of effort in controlling variables so I got a lot of auxiliary equipment for brewing with the robot like a lunar scale, Comandante grinder, fellow temperature control kettle, third wave water additive, WDT tool and more so I could pick at individual variables to adjust with relatively fine control. This is not to say that you need all of those but perhaps experimenting with different aspects is easier for me than for you because I have more “measurements” with every shot. Regardless, I really do think you made the right choice with the Robot even after watching all the videos from James for a year. You have the ability to change and control everything about your espresso with that little guy. As deep as I fell into the espresso rabbit hole, I didn’t have any regrets about getting a different machine. As long as you keep putting in the effort on the arms you will get a to a point that you can make espresso better than the coffee shop.

[@haberdashery314]

​@@SnowBob302 So nice to have my choice validated, and thanks for the pointer to the user group. From all I had read before buying, Robot is the cheapest way to make first rate espresso. Flair seems to be good too, but workflow looked fussier. My only regret is that I didn't buy mine in time to get polished aluminum. Still beautiful in colors. Mine is Red. My wife said she thought it should be in MOMA (museum of modern art in New York). You cant say that about any other machine under $500. I Fixed my comment on pressure. thanks

[@lucask4865]

Hey James, the new "Flair 58" got leaked, can you get your hands on one and review it if possible? I think this has to be a massive improvement over the flair pro 2! Cant wait for your opinion on it.

[@alanherrera5421]

Feeling more barista with every video, thanks for explaining such a great topic!

[@metangas5]

While I really relax and enjoy learning from your videos, despite me not even currently liking the few espressos I've had locally yet, I'm now focusing on and distracted by your assortment of what looks to be amaros on that bar table behind you

[@jca7991]

Every time I see that 70s Melitta set in the background of one of James’s videos, I just fawn 🥺

[@yannickkops1959]

I have been playing with different pressure profiles on my flair and tasted different results. But finally understanding the theory behind it. Thank you!

[@sunflowerdeath]

This is a great explanation. I think that basket size and shape, and depth of a puck are also related to optimal pressure.

[@Nonaps512]

I am in the market of a new machine and was wondering how important a pressure gauge is. This epesode really helped . Just settling on an Oscar 2. Thanks to this channel my mornings and coffee ritual will be better off.

[@sammu]

Beautifully presented material as usual. Thanks James!

[@beck2929]

One potentially interesting proposal for future videos: since there are many single people and would like to avoid waste of coffee when having single shots, would be great to have a comparison video on how to properly pull single shots with single filters, usually inconsistent and potential workarounds (like pulling a single shot from a double filter). Thanks!

[@Pappderbarp]

4:05 i have Illy's book at home, highly recommend it for getting really nerded out

[@joseandrade256]

This was very interesting, but I guess hard for most people to apply in practice. For example, I have a Barista express and I noticed that the pump is set, broadly speaking, to a constant flow output (its not entirely linear, specially at either end (very very coarse, and very very fine) but close-ish to it). I guess this is the type of pump in the machine, it has a mechanism that will push water at a constant rate and whichever pressure builds up on the opposing side is irrelevant, only being stopped at the point at which the over-pressure valve is set to. Now, I think that, just like electronic circuits, pressure, flow and resistance to flow are all linked together. What happens is that as you grind finer, you increase puck resistance to the flow and the pressure increases if flow stays roughly the same. What then happens is that you are somewhat forced to use their original recipe and hit brew time and volumes as they dictated. In practice, the pump does not really provide a constant flow as the pressure increases, probably because that requires much more power, that the pump does not have, so you do end up having a slight decrease in flow as you go towards higher pressure. But this is not ideal: ideally you want a certain pressure delivered to your coffee, and then the flow is dictated by the resistance of the puck (although, like James said when explaining why 9-Bar, the pressure-flow relationship is not 100% linear either, but that does not invalidate that at least a machine should provide above all, controlled pressure). This is not like flow-profiling where the machine/person carefully select a target flow. After writing all this however, I notice that the pump, might also be instead a constant power pump, which would mean that there is an inverse relationship between flow and pressure, and their product stays constant, but I think its more a mix between the 2: constant flow and capped power. But now, all this just to say, that some pumps can deliver 9 bar, or 12 bar, or 15 bar, and that pressure will only depend on how much resistance the coffee is giving while the flow is only marginally affected, instead of having 9-bar delivered and the shot flowing because of those 9-bar. Another thing, pertinent to the barista express, is that the portafilter is smaller in diameter. Now about this topic, I have been thinking a lot, about all its effects, but I cannot attest any of this. Lets consider the case where I want to mimic a recipe done in a commercial 58mm portafilter machine: have a fixed brew ratio of 2:1, 18g in, 36g out, for 30s. First we see that flow needs to be the same. But the puck height is greater, which to me, I guess, for the same grind setting would mean a higher resistance. So now we see that for the same flow to happen, for same pressure, we need to grind coarser. This, in principle, would mean a lower extraction I guess? I would imagine that dialing in, if wanting to keep the same dose and yield would mean that both time and grind setting would need to be adjusted for the difference in puck thickness. To say, that it also becomes non-trivial to replicate recipes with machines with different portafilter sizes....or I might just be incredibly wrong and some variables just cancel each other out. Lastly, I want to say, that at some point I will hack my machine and change its over pressure valve to limit the pressure to 9~10-bar, but that this is not something everyone could easily do, or should do as it voids warranty, etc.

[@diganta2329]

Fantastic video. Lots of insights that not many people can share in that way. Thank you!

[@slvrbach]

This is probably the BEST James Hoffmann video I've seen! Thank you for breaking it all down and reaffirming that my assumptions about pressure/flow line up with the conventional understanding of how it's generally supposed to work! 👍

[@andreavon5929]

A really interesting and informative video. On my machine with darker roast I have no channelling, but lighter roast it is something else, the pressure could be the answer, I might need Bianca

[@GoTellJesusSaves]

Thoroughly enjoyed this series, as I am learning to make great espressos.

[@xXAtmosphere]

I missed this series. Thanks for bringing it back!

[@kweenamora2103]

Watching and learning more for my small coffee shop that will be launch on 2024 ☺️

[@Tyraendiel]

That topic made so many geotechnician, civil engineer, or other kind of engineer think about it in the comment section. The three state of the soils, capillary effects, Darcy's law, consolidation, OCR factor, hydrostatic pressure gradient, etc. So much knowledge that we can provide to the topic and maybe figure out something new about espresso making. I was so happy to read them through. We should test some coffee pucks as soil samples for the mechanical properties, so we can maybe calculate some of the inputs for the desired outputs.

[@daniwalmsley611]

I feel like the decents party trick is rarely talked about. And thats it's ability to recreate lever shots. If you add the smart espresso profiler to your lever machine you can recreate that perfect shot again and again on the decent

[@kurniawanputra9312]

I used flair classic. I used pressure as a guide for grinder size, the harder pressure mean the finer the grinde size. Usually the harder the pressure, finer grinding size, get better espresso (according to me), yet it's true, tends to oftenly produce more channeling. Now, i still struggles on this.

[@_mickmccarthy]

Hands down the best machine I've worked with (in terms of consistently great espresso) was a sprung lever machine. I love my fully manual La Pavoni, but it's not (well, I'm not) as consistent as a sprung machines. Definitely a step up from the pump-driven machines I've worked with.

[@GraemeRobinson]

Flow and pressure are of course two sides of the same coin and I would argue flow has always been a consideration in the argument between constant pressure pump or traditional lever machine. The E61 has a design feature that to some extent helps the barista jockey flow. The middle lever position turns off the pump without releasing pressure. I use this to slow flow towards the end of a shot if it increases too rapidly, in order to 'save' the shot, moving it up to turn the pump back on when flow ebbs and back to the middle. In the same way as lever machines pressure could be jockeyed by holding back the release of the spring. Excellent video - I learned much thanks.

[@anselmoverissimo7512]

Amazing knowledge… glad his channel appeared in my feed… KZbin makes it right sometimes.

[@kerryburt9498]

I had been hoping that you would do a video on this subject. Thanks for demystifying some of these more esoteric topics!

[@taniknight]

Excellent content, as always. Many thanks. I have 2 comments on pressure. Firstly, I rarely hear it mentioned but there is necessarily another pressure profile in the form of the pressure change through the depth of the puck, from brew pressure to atmosphere pressure as it leaves the basket. I have no idea what sort of curve this profile would follow but if we accept that it would not be a step change right at the basket then not all of the coffee experiences brew pressure anyway. This crossed my mind many years ago when operating an Izzo Groupo lever machine with deeper and narrower baskets (can’t recall the dimensions), wondering how that affected channeling and pressure profile through the puck. My second comment shared my experience working commercially with the above mentioned spring lever machine. Of the brew process that was in the barista’s direct control, I found that the TRANSITION from pre infusion to brew pressure has dramatic effects on the coffee output. Keeping all else equal, a transition of say 2 seconds would make a tasty shot but shortening that to less than 1 second would result in very low flow and a huge brew time. Thus, if we dialled in using a 2 sec transition we could grind finer and make tasty beverages. By the way, I and my staff used that lever machine in our cafe for over a year, averaging 400 coffees a day and peaking at about 700 on crazy days. Temperature control was tricky but it was quite spectacular to watch and customers loved it.

[@RobertsonDCCD]

As a newcomer to semi-automatic espresso brewing, I have learned a lot from this series. I am pulling shots now on a Lelit Bianca, which offers both automatic preinfusion and manual profiling with a paddle. I am at stage where I really enjoy the puck preparation stage, but once I throw the lever, it all goes so fast! Watch for the initial pressure, see when the first drops appear, ramp up the pressure, watch for channeling, but don’t forget to watch the scale to catch your desired yield. Finally, record the time, taste the shot, and try to remember what went right and wrong for the next attempt. I am looking forward to the day when it all slows down and becomes more natural. That will come, right?

[@jameson1895]

You’re not alone - so much to watch, so little time!

[@bazza945]

James is back - under pressure.

[@transmogrifiers]

I like to brew at pressures way above 9 bars on very finely ground coffee. I put nearly all my weight on the Flair Classic lever. It allows for very strong shots without the bitterness. On freshly roasted grains, it also converts crema into oil, litterally, that you see floating on the coffee, and that tastes incredibly good. The downside is that it's a drop by drop extraction, and you have to be patient. Another aspect of pressure is that if you don't have a distributor or tamper you can uniformly compress the puck by "punching" it with high pressure before you start preinfusing at lower pressure. This all may be quite unorthodox so I would be interested in other opinions.

[@cadenlee2365]

I'm using a flow control machine for my daily coffee which is DC Mina, the pressure of this machine is fixed at 9 bars, but you can have full manual control on flow rate by a digital flow regulator up to 5 step, by using naked portafilter, I start to see the channeling happen if we keep the common flowrate around 8-10g /sec and if we low down flow rate when the live coffee pressure in the basket & group head meet the peak and pressure start to decrease, the live flowrate pass through the coffee also start to increasing and we can start to reduce flow rate to slow down the output flow and for few years of experimental, i think it's quite good to control for repeatable brew for consistency, in result I get lesser fine come into the espresso and more higher flavor clarity in the espresso, but in result compare to other machine i have, the body is slightly reducing.

[@sebas9504]

Amazing video, James!! You consistently produce such high quality, informative content and the coffee world is lucky to have you